/**
 * 
 */
function bind(fn, context) {
    return function() {
        return fn.apply(context, arguments);
    }
}

var btn = document.getElementsByTagName('button')[0];
var p = document.getElementsByTagName('p')[0];

function demoFn() {
    console.log(arguments, this);
}

btn.addEventListener('click', function() {
    // do sth
})

var bindFn = bind(demoFn, btn);

var bindFn = bind(demoFn, p);

btn.removeEventListener('click', bindFn)
